6665561 has 16 divisors (see below), whose sum is σ = 8371200. Its totient is φ = 5174928.

The previous prime is 6665539. The next prime is 6665567. The reversal of 6665561 is 1655666.

6665561 = T₂₀ + T₂₁ + ... + T₃₄₁.

It is a cyclic number.

It is not a de Polignac number, because 6665561 - 2⁶ = 6665497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6665567) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1970 + ... + 4148.

It is an arithmetic number, because the mean of its divisors is an integer number (523200).

Almost surely, 2^6665561 is an apocalyptic number.

It is an amenable number.

6665561 is a deficient number, since it is larger than the sum of its proper divisors (1705639).

6665561 is a wasteful number, since it uses less digits than its factorization.

6665561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2228.

The product of its digits is 32400, while the sum is 35.

The square root of 6665561 is about 2581.7747771640. The cubic root of 6665561 is about 188.1968004793.

The spelling of 6665561 in words is "six million, six hundred sixty-five thousand, five hundred sixty-one".